Display screen or portion thereof with a graphical user interface



FIG. 1 is a front view of a first image in a sequence of a display screen or portion thereof with a graphical user interface that has the new design; and,

FIG. 2 is an enlarged front view of a second image of the sequence of the graphical user interface, shown without the broken line environment for clarity of disclosure.

The appearance of the animated image sequentially transitions between the images shown in FIGS. 1 and 2. This process or period in which one image transitions to another forms no part of the claimed design.

The outermost broken lines in FIG. 1 illustrate the environment of the design and form no part of the claim. The remaining broken lines, including all text, illustrate portions of the display screen or portions of the graphical user interface that form no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with a graphical user interface, as shown and described. 